A light emitting diode (LED) that is a semiconductor light emitting device using semiconductor layers has characteristics such as a small size, high power efficiency and fast on-off responsibility, as compared with conventional light emitting apparatuses such as traditional fluorescent lamps and incandescent lamps, and since the diode is all formed of solid, has many advantages such as high resistance to vibration and long apparatus life.
In addition, in the LED, the center emission wavelength is a single, the single wavelength is limited in its use to use as various kinds of light sources, and therefore, as an emission light source, white light is required.
For example, Patent Document 1 discloses the invention related to a semiconductor light emitting device for generating white light by combining a blue LED and a fluorescent material which absorbs the emitted light to emit yellow fluorescence, and mixing the yellow light and blue light that is not absorbed.
Further, Patent Document 2 discloses the invention related to a white LED lamp having a light emitting diode chip that emits first light of UV light to violet light and a transparent resin layer with a fluorescent material layer dispersed. When the first light passes through the transparent resin layer and arrives at the fluorescent material layer, the fluorescent material powder inside the fluorescent material layer emits light (second light) such as blue light, green light, yellow light and red light, and at this point, it is determined that the color of light obtained by mixing respective colors of the second light is white.
Patent Document 3 discloses the invention related to a semiconductor light emitting device that is one component of a semiconductor light emitting apparatus. It is mentioned in Patent Document 3 that a concavo-convex pattern of micro-order is provided on the substrate surface forming an LED, and that the waveguide direction of light in a light emitting layer is changed to enable the light extraction efficiency to be improved. In addition, also in the invention as described in Patent Document 3, it is mentioned that a fluorescent material including YAG is mixed with a resin and formed on the surface of the semiconductor light emitting device to enable a white light emitting apparatus with high light extraction efficiency to be obtained (see paragraph [0077], etc. in Patent Document 3).
Patent Document 4 discloses a light emitting apparatus with high light extraction efficiency by forming a concavo-convex structure on a light emitting exposed surface of a semiconductor light emitting device, and coating with a coating layer including fluorescent materials.
Further, Patent Document 5 discloses a semiconductor light emitting apparatus in which a light extraction layer made of resin material with a concavo-convex structure formed on its surface is provided on a layered semiconductor layer including a light emitting layer.
Furthermore, Patent Document 6 discloses the invention related to a substrate for semiconductor light emitting device and semiconductor light emitting device in which a pattern of nanosize is provided on the substrate and the pattern is provided with a long period of micro-order. According to Patent Document 6, it is mentioned that it is possible to suppress crystal defect dislocations in epitaxial growth in manufacturing an LED and to increase the internal quantum efficiency of the LED, the light extraction efficiency is also increased by providing the long period of micro-order, and that as a result the external quantum efficiency, which is defined by the product of the internal quantum efficiency and the light extraction efficiency, is also enhanced.